Register control system for web cutting mechanisms



June 3, 1952 R. A. BEUERMAN 2,599,430

REGISTER CONTROL SYSTEM FOR WEB CUTTING MECHANISMS Filed March 29, 1950 b J5 1 if INVENTOR.

RALPH ALBERTS BEUERMAN FORWARD J -R ETARD SCANNER ATTORNEY Patented June 3, 1952 REGISTER CONTROL SYSTEM FOR WEB CUTTING MECHANISMS Ralph Alberts Beuerman, Kenmore, N. 35., assignor to E. I. du Pont de Nemours and Company, Wilmington, DcL, a corporation of Delaware Application March 29, 1950, Serial No. 152,742

1 Claim. 1

This invention relates to automatic control systems applicable to continuous web cut-off mechanisms, and more particularly to an improved system for controlling and maintaining the operation of web-feeding and the web cut-off means in predetermined register.

In modern package-making machines, in which articles or materials are enclosed in wrappers which are cut from webs of paper or similar materials, it is usual to cut a succession of single wrappers from a web on which is provided a succession of imprints or designs (one design for each wrapper) spaced at an equal distance from each other. It is usually required that in each of the wrappers thus cut, the design shall occupy an exact predetermined position on its wrapper in relation to the line of cutting; i. e. the printed design must be kept in register with the cutting mechanism.

When the web has been printed and wound on a roll to be fed later into a packaging machine, there is no definite relation between the actual printing and the roll which feeds the web mto the machine. The slightest error in the relation between the feed roll travel per cutter operation and the spacing of the printing on the web will result in cutting through the printed design. For example, even though this error should be only of 1%, after 500 sheets have been run, the cut will Occur in the middle of the sheet rather than at the correct point-and on high speed machines it requires only a short time to cut off 500 sheets.

Heretofore the problem of register control has been attacked mainly from the standpoint of exercising control over the feed of the web in order to bring the cut-off into predetermined register. Such controls, however, are inapplicable to the cutting of webs fed directly from a printing press or like web-handling machinery operating at constant speed. Moreover, in devicesheretofore proposed and/or used the mechanisms have been such that corrective operations responsive to offregister conditions have been too slow to provide satisfactory cut=ofi register control on high speed machines.

Therefore, an object of this invention is to provide an improved and simple means for controlling the register of a web at the point of severance.

Another object is to provide an improved web cut-ofi register control means useful on highspeed continuous web feed machines.

Still another object is to provide a web cutoff control means which is more rapidly responsive to out-of-register conditions than are the cut-off control means heretofore known.

A still further object is to provide in a device for continuously cutting printed bands from a web having printed thereon unit designs, cut-off register control means operative to maintain the cutter knife in synchronization with the unit design printed on the web.

These and other objects will more clearly appear hereinafter.

These objects are accomplished by my invention which, briefly stated, comprises providing separate electric motors for driving the feed rolls and the cutter knife, respectively, of the usual web-cutting mechanism, correlating the relative speed of the motors to secure cut lengths of the desired measure by coupling the feed roll drive motorwith a tachometer generator and employing the electric power so generated (having a predetermined reference voltage which is, of course, directly related to the speed of the drive rollmotor) for driving the cutter motor. Substantially instantaneous correction of out-of-register conditions is provided by increasing or decreasing the normally constant reference voltage applied to the cutter motor, responsive (preferably by means of photo-electric devices) to out-of-register conditions of the web relative to the point of cut whereby the cutter motor speed is increased or decreased to bring the cut back into register.

My invention, in a preferred modification will now be more specifically described with reference to the accompanying drawing wherein:

Fig. 1 is a schematic view illustrative of the cut-oif register control system of this invention;

Fig. 2 is a diagrammatic sketch of the selector switch;

Fig. 3 is a front elevation showing an illustrative disposition of the openings in the rotating disc element of the phase detector; and

Fig. 4 is a diagram showing the time phasing of the electrical pulses from the phase detector and the photoelectric scanner.

Referring to Fig. lthe pre-printed web material I, either unwinding from a roll or coming directly from a printing press, etc., is pulled under the photoelectric pickup device or scanner 2, printed surface up, by driven feed rolls 3 and is then thrust between the rotating knives 4 which cut it off in the correct length, with the printing properly registered. The photoelectric pick-up or web scanner 2 is of conventional design and comprises a light source which is projected onto the printed surface of the tubing by means of an optical system. This light is reflected and picked up by another optical system, which projects the reflected light onto a photoelectric tube. Any interruption or variation in reflected light will affect the output of the photoelectric tube, whose signal is pre-amplified in the photoelectric pick-up head and then transmitted to an electronic mixing and integrating device 5 of conventional design (shown in Fig. 16 of pamphlet GEE-1429A, published by General Electric Company, Schenectady, N. Y.). Th feed rolls 3 are driven by an independent motor 6 operated from a conventional motor control panel 9. This same motor also drives a D. C. tachometer generator 1. The current from the generator passes through a ratio control 8 and the current from 8 at a pro-determined reference voltage directly proportionate to the speed of motor 6 is then passed to the input of an amplidyne generator I (such as is described in an article entitled Torque and speed "regulation with the electronic amplidyne in Electric Manufacturing, July 1948) which in turn supplies power to an independent cutter drive motor H which drives rotating knives 4. When the speed of the feed roll motor changes, thus changing the voltage from the tachometer generator, the ratio control automatically changes the reference voltage to the amplidyne generator in proportion, so that the cutter drive motor speed changes accordingly. Thus, regardless of the speed of the feed roll motor, the speed of the cutter motor will be in phase therewith and hence will always out sheets of the same length. An added feature of this type of a drive for the cutter, is that when the feed roll motor stops, the cutter motor will also stop. The ratio control is simply a voltage control device which enables one to preset the reference voltage in a predetermined ratio to the voltage applied to the motor whereby sheets of any desired length may be cut. The reference voltage from the ratio control is supplemented in the input of the amplidyne generator by the current from the mixing and integrating device 5, which varies according to the location of the design on the web. As is more fully described hereinafter, any change in location of the design is instantly reflected by the output of the mixing and integrating device to the amplidyne, and in turn to the cutter drive motor.

Correction of the speed of cutter motor ll rcsponsive to out-of-register conditions of the printed web is obtained by feeding a small plus or minus voltage to the input of the amplidyne generator from the output of the electronic mixing and integrating device 5 the input of which is supplied from the photoelectric scanner 2 and a phase detector unit 12. Referring to Figs. 2 and 3 a suitable phase detector unit I2 (described in pamphlet GEE-1429A, published by General Electric Company, Schenectady, N. Y.) comprises essentially a light source l3, two photoelectric tubes Hi and I5 which are positioned to receive light from source l3 through two suitable optical systems (not shown), and a slotted rotating disc l6 positioned between the light source and the cells to interrupt the light therebetween. Light source l3, tubes [4 and i5, and the accom panying optical system are preferably rotatably mounted as a unit for adjustment with respect to disc I6. The disc [5 is directly driven by cutter motor I l and is provided with two staggered slots l4 and I5 aligned with tubes l4 and [5 respectively so that the light will pass through each slot to its aligned tube and activate the latter once for every revolution of the disc. The slots are so positioned, one with respect to the other, that the distance or dead zone (a in Fig. 3) between the slots is slightly greater than the width of the printed band on the web, and the speed of the cutter is'adjusted relativ to the speed of the web so that in normal operation light passes thru one slot and energizes its photoelectric tube just before the design is scanned by the scanner and passes thru the other slot and energizes its tube just after the design is scanned by the scanner. Thus one slot controls the forward phase and the other slot controls the retard phase of the correction cycle. The electrical pulses from the tubes are preferably preamplified and are then fed into the input of the electronic mixing and integrating device 5 which, as stated hereinabove, is of conventional design and comprises essentially two double grid mixer power tubes (6V6) feeding a 1:1 ratio transformer.

It will be apparent from the foregoing that when the cutter and the design on the web are in register for proper cutting an electrical pulse or signal of positive polarity from one photoelectric tube of the phase selector will be fed into the electronic mixer and integrator 5, followed by a pulse of positive polarity from the scanner 2, which pulse is followed in turn by a pulse from the other photoelectric cell of the phase selector which is converted by an electronic tube to a pulse of negative polarity. The time pattern of this signal sequence for every revolution of disc i6 is diagrammed in Fig. 4. As long as the pulses are fed into '5 in the order described the signal input to the grids of the mixer tubes will not coincide; hence, no current will pass and the output from 5 will be zero, and the cutter motor I! will be driven by the output from the amplidyne generator controlled by the predetermined reference voltage only as described hereinabove. However, should the scanning signal or pulse be out of phase and overlap or coincide in time with one or the other pulse from the phase detector the input into the grids of the mixer tubes of 5 will coincide and a plus or minus current, depending on whether the retard or forward pulse from the phase detector coincides with the signal from the scanner, will be delivered to the electronic controlled D. C. power supply or high gain multiple field generator such as the amplidyne, thereby increasing or decreasing the output of the latter to speed up or slow down the cutter motor and thus bring the cutter and web design into register.

While the control system hereinabove described is obviously applicable to the cutting of almost any web material customarily cut into shorter lengths, it is particularly applicable to high speed operations such as the cutting of shrinkable printed bands from printed tubing of regenerated cellulose where accurate registration of the printed design on the band is required and very close tolerance limits in cutting must be observed.

The cutter may, of course, be of any suitable and/or convenient design such as a rotary. straight knife edge, reciprocating, etc. likewise the electric and electronic equipment employed need not be restricted to the designs hereinabove described since it is apparent that a variety of electronic devices available to the art may obviously be employed with the same eiiect without departing from the spirit of my invention.

I claim:

Apparatus for continuously cutting predetermined lengths from a web having a succession of like designs or indicia thereon, the point of cut being in register with the design or indicia, comprising in combination a cutter blade, an electric cutter motor driving said cutter blade cooperating positively driven feed rolls positioned to feed to said cutter blade continuous web having a succession of spaced designs or indicia thereon, an electric feed roll motor driving said feed rolls, a tachometer generator driven by said feed roll motor operative to generate a current of a reference voltage directly proportionate to the speed of said feed roll motor, an electronic amplidyne generator energized by said current at said reference voltage and arranged to furnish electric power of predetermined voltage to operate said cutter motor at a constant speed which is in predetermined ratio to the speed of the feed motor whereby to cut lengths of web of predetermined size from the continuous web, photoelectric tube web scanning means operative to indicate the position of the web, photoelectric tube means operatively associated with said scan ning means to indicate the position of the cutter blade at the time of cut relative to said design and responsive to out-of-register condition to pass a current of negative polarity into the input of said electronic amplidyne generator, whereby to retard the speed of the cutter motor by reducing the voltage applied thereto, photoelectric RALPH ALBERTS BEUERMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Cordes Mar 30, 1937 Number 

